**África Sanchiz, Esperanza Morato, Alberto Rastrojo, Esther Camacho , Sandra González-de la Fuente, Anabel Marina, Begoña Aguado and Jose M. Requena \***

Centro de Biología Molecular "Severo Ochoa" (CBMSO, CSIC-UAM) Campus de Excelencia Internacional (CEI) UAM+CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain; africa.sanchiz@gmail.com (Á.S.); emorato@cbm.csic.es (E.M.); arastrojo@cbm.csic.es (A.R.); ecamacho@cbm.csic.es (E.C.); sandra.g@cbm.csic.es (S.G.-d.l.F.); amarina@cbm.csic.es (A.M.); baguado@cbm.csic.es (B.A.) **\*** Correspondence: jmrequena@cbm.csic.es

Received: 27 July 2020; Accepted: 28 August 2020; Published: 2 September 2020

**Abstract:** *Leishmania infantum* causes visceral leishmaniasis (kala-azar), the most severe form of leishmaniasis, which is lethal if untreated. A few years ago, the re-sequencing and de novo assembling of the *L. infantum* (JPCM5 strain) genome was accomplished, and now we aimed to describe and characterize the experimental proteome of this species. In this work, we performed a proteomic analysis from axenic cultured promastigotes and carried out a detailed comparison with other *Leishmania* experimental proteomes published to date. We identified 2352 proteins based on a search of mass spectrometry data against a database built from the six-frame translated genome sequence of *L. infantum*. We detected many proteins belonging to organelles such as glycosomes, mitochondria, or flagellum, as well as many metabolic enzymes and many putative RNA binding proteins and molecular chaperones. Moreover, we listed some proteins presenting post-translational modifications, such as phosphorylations, acetylations, and methylations. On the other hand, the identification of peptides mapping to genomic regions previously annotated as non-coding allowed for the correction of annotations, leading to the N-terminal extension of protein sequences and the uncovering of eight novel protein-coding genes. The alliance of proteomics, genomics, and transcriptomics has resulted in a powerful combination for improving the annotation of the *L. infantum* reference genome.

**Keywords:** *Leishmania infantum*; proteome; post-translational modifications (PTMs); proteogenomics; mass spectrometry
